Method and apparatus for production of a reinforcement bar

ABSTRACT

A method for fabrication of a bent reinforcing rod in a composite material is described, where the reinforcing rod is composed of longitudinal fibers and a sheathing layer of fibers or foil, comprising the steps: to moisten fiber thread with a binding agent, to reel the moistened fiber thread to a bundle with a closed, approximately circular shape, consisting of a layer of longitudinal, parallel fibers of a desired thickness, whereby all the fibers in the layer obtain an approximately equal axial tightening, and to envelope an outer layer of fiber threads, and/or foil, or other suitable material, around the layer of longitudinal fibers, and that the fabricated blank is given a final form in a second forming process. The invention also relates to a device ( 10 ) for carrying out the method.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage application under 35 U.S.C. 371 ofPCT/NO2004/000185, filed on Jun. 23, 2004.

The present invention relates to a method and a device for fabricationof a reinforcing rod in a composite material, where the reinforcing rodis composed of longitudinal fibres and a sheathing layer of fibresand/or foil, or other suitable material.

In particular, the present invention relates to composite rods in a bentconfiguration for use in concrete, among other things. Such bends have alimited size, and normally have a U-shape, an angle shape or acombination of these. The designation for such bent rods is loops. Aproblem with known composite rods is that tension differences arise inthe bent areas. This is due to different tightening of the fibre threadsin the bent areas. In the bending of the known rods, the outer fibrethreads will thereby be stretched more than the inner fibre threads. Thechallenge is therefore to fabricate a composite rod where the fibrethreads have an approximate even tightening in the inner part of theloop as well as in the outer part, i.e. in the bent parts also. This isvery important for the strength of the composite rod.

From known technology, U.S. Pat. No. 5,981,630 shall be mentioned amongothers. This document concerns sine-formed small fibres for mixing inwith the concrete. U.S. Pat. No. 4,620,401 relates to winding of anordinary composite rod for establishing an anchorage in the concretewith a loop, that is produced by winding on a body, and cured. EP0308237 concerns a production process for straight rods, but withdifferent cross-sections that are established by fabrication of a rodwith a circular cross-section. Of these documents, this is closest tothe present invention, namely in that the profile is formed in anuncured condition. However, it is difficult to obtain even tightening inthe fibres after forming in the rectangular, L, H or I cross-section asshown in the document. Besides, EP 0308237 relates only to cross-sectionforming of straight rods, and not loops as with the present invention.

Whatever the desired shape of a loop, it can be fabricated in a whole,closed form. A circular blank can thereby be used to be formed into adesired shape. If the final product shall not have a closed shape, twoor more products can be combined and after the shape has been completedand cured, it can be divided. If an angle shape only is wanted, two orfour angles can be combined to a square shape that has a closed form.Thereafter, it can be cut at two corners to make two angle loops, or atthe sides to make four angle loops. If a U-shape is wanted, one can dothe same, i.e. make a complete square and divide it into two afterwards.

A circular blank, for example, where cured plastic covered fibres arereeled into a bundle on a holding device, where the fibres are equallytight, will have the shorter fibres nearest the centre and the longer onthe outside. In subsequent shaping of the circular blank into any shape,i.e. in one and the same plane, one achieves that all the fibres areequally tight. The assumption is that the fibres glide axially inrelation to each other during the shaping to adapt to the forminglocally.

The object of the present invention is to provide a bent reinforcementrod in a composite material that does not have the abovementioneddisadvantages and which has equally tight fibres in the bent sections asin the rest of the rod. Thereby, one achieves that whatever the shapethe composite material is bent into, the fibres will lie approximatelyin parallel.

The object is achieved with a method of moistening fibre thread with abinding agent, to reel the moistened fibre thread into a bundle with aclosed, approximately circular shape, comprising a layer oflongitudinal, parallel fibres of the desired thickness, whereby all thefibres in the layer get approximately equal axial tightening, and toenvelope an outer layer of fibre threads and/or foil, or other suitablematerial, around the layer of longitudinal fibres, whereupon thefabricated blank is given a final shape in a second forming process.

In alternative embodiments of the method the enveloping can comprisewinding, by a method in itself kinown, an outer layer of fibres threads,and/or foil/band, in a helically form around the layer of longitudinalfibres, or the enveloping can comprise knitting, by a method in itselfknown, an outer layer of fibre threads, and/or foil/bank, around thelayer of longitudinal fibres. The moistened fibre thread can be woundinto a bundle by reeling of the fibre thread onto a rotational platewith a number of holding means for fibre thread, to the approximatelycircular form. The final shape of the reeled bundle is preferablyobtained by tightening in a gig to the desired form, and by thesubsequent heating to the curing temperature for the binding agent,whereupon the finally formed blank can be divided. It is preferred thatthe used fibre thread is selected from a group comprising glass, basalt,carbon, thermoplastic or the like, and cured plastic is utilised as thebinding agent.

The invention also relates to a device for carrying out the methodaccording to the invention, and is characterised by a device for reelingand winding of fibre threads for use in reinforcing rods of a compositematerial, with a rotational plate comprising a number of holding meansfor Fibre thread, where the holding means are arranged at a mutualdistance apart adjacent to the outer edge of the plate, for reeling ofan approximately circular blank with longitudinal fibre threads.

Alternate embodiments of the device are characterised in that theholding means are wheels encompassing suitable grooves for the fibrethreads, and that the device comprises a winding appliance arranged forwinding fibre thread, and/or foil, or other material, in a helicallyform around the longitudinal fibre threads, or that the device comprisesat least one knitting appliance arranged to knit fibre thread and/orfoil, or other suitable material, around the longitudinal fibre threads.The device can also comprise a tightening system arranged to tighten andto regulate the supply of fibre thread to the holding means of therotational plate.

The invention shall now be described in more detail with the help of theenclosed figures, in which:

FIG. 1 shows an embodiment of a device, according to the invention, forreeling of fibre threads.

FIG. 2 shows a winding process of helically coiling of an outer layer offibre threads and/or foil.

The principle of the present invention is that moistened fibres arearranged in a circular bundle. These are kept in a bundle form with thehelp of a sheathing of wound or knitted material, fibres, foil, band orthe like, suitable for keeping together the fibres in the circularbundle. The material being wound round can also be selected with regardto the surface of the final product, as a surface well suited toachieving a good grip between the reinforcing (the loop) and theconcrete. The bundle is preferably circular to achieve an eventightening in all fibres after the bundle has got its final shape and isto be cured.

In forming of the pre-produced loop (bundle) in a final shape, thefibres will glide longitudinally with respect to each other to adapt tothe shape the loop will be given, but this is locally and the finaltightening will be equal for the inner and outer fibres, as long as thefinished loop has a continuous, closed form in one plane.

The advantage with this production process is that one does not need anyspecial form where the loop is produced and cured. It can be made readyin blanks, which then are formed in simple gigs and are cured. It isonly required that the blank must be of about the right length(circumference) and that the cross-section is right (material diameter).The shape is decided by the tightening jig in the curing only. Thisfinal shape and the curing can take place over days to weeks after theblank is produced.

Furthermore, it shall be mentioned that another form for sheathing ofthe fibre threads other than coiling can be used also. For example, thefibre threads can be knitted by crocheting or sewing, or the like. Theadvantage of knitting rather than coiling is that the fibre bundle isnot stressed by a moment corresponding to that during the coiling.

FIGS. 1 and 2 show a device for fabrication of blanks of compositematerial which shall be formed to reinforcing loops to be used in, forexample, concrete. As shown, the device 10 comprises a rotationalplate-like part 12 comprising a number of holding means 14 for the fibrethreads. The holding means can be shaped as wheels with suitable groovesfor the fibre threads. The wheels can, if required, be rotary. Therotational plate 12 rotates with the help of a driving appliance, suchas a standard electromotor or the like.

The fibre threads are reeled to a bundle in that the plate-like partrotates. Control of the tightening in the fibre threads can be obtainedby a tightening appliance 16, arranged adjacent to the plate-like part12. The tightening appliance can comprise a wheel 18 which alsoregulates the application of the fibre thread, and the wheel canalternatively be spring-loaded to further regulate the tightening in thefibre thread.

Prior to the reeling of the fibre thread, a binding agent is applied toit, preferably in the form of a thermoset plastic, by the fibre threadbeing led through the binding agent or brought into contact with thebinding agent in another way.

After the longitudinal, parallel fibre threads are reeled into a bundle,they can be held together by helically winding of an outer fibre thread,and/or a foil, or other suitable material, with the help of one or morewinding appliances 18, 20 for fibre thread and foil/band, respectively.

In an alternative embodiment of the device according to the invention(not shown), the longitudinal, parallel fibre threads, after beingreeled into a bundle, can be held together by an outer fibre thread,and/or a foil, or other suitable material, being knitted on with thehelp of one or more knitting appliances for fibre thread and foil/band,respectively.

Thermoset plastic is initially applied as a binding agent, but it isalso possible to use thermoplastic as a binding agent. The process willbe the same, while the working operations reeling/winding and finalforming must necessarily take place at a temperature where thethermoplastic is liquid to a sufficient extent. The curing itself willthen be unnecessary, only cooling must be carried out.

1. A method for fabrication of a reinforcing blank from a compositematerial, wherein the reinforcing blank is fabricated of longitudinalfibres and a sheathing layer of a material selected from the groupconsisting of fibre and foil, and wherein fibre thread is moistened witha binding agent, comprising the following steps: reeling the moistenedfibre thread onto a rotational plate comprising a number of holdingmeans for fibre threads, to a blank bundle in a closed, approximatelycircular shape, comprising a layer of desired thickness of longitudinal,parallel fibres, whereby all longitudinal, parallel fibres in the layerachieve approximately equal axial tightening; enveloping an outer layerof a material selected from the group consisting of fibre threads,foil/band and mixture thereof, around the layer of longitudinal fibres;and finishing the fabrication of the prepared blank in a second formingprocess, wherein said enveloping comprises winding on itself, an outerlayer of a material selected from the group consisting of fibre threads,foil/band and mixture thereof, in a helical form around the layer oflongitudinal fibres.
 2. The method of claim 1, wherein the final formingof the reeled bundle is carried out by tightening in a jig to therequired shape and by subsequent heating to the curing temperature ofthe binding agent.
 3. The method of claim 2, wherein the finally formedblank can be divided in two or more parts.
 4. The method of claims 1,wherein the fibre thread is selected from a group consisting of glass,basalt, carbon, and thermoplastic.
 5. The method of claims 1, whereinthermoset plastic is used as a binding agent.
 6. The method of claims 1,wherein thermoplastic is used as a binding agent.
 7. A method forfabrication of a reinforcing blank from a composite material, whereinthe reinforcing blank is fabricated of longitudinal fibres and asheathing layer of a material selected from the group consisting offibre and foil, and wherein fibre thread is moistened with a bindingagent, comprising the following steps: reeling the moistened fibrethread onto a rotational plate comprising a number of holding means forfibre threads, to a blank bundle in a closed, approximately circularshape, comprising a layer of desired thickness of longitudinal, parallelfibres, whereby all longitudinal, parallel fibres in the layer achieveapproximately group axial tightening; enveloping an outer layer of amaterial selected from the group consisting of fibre threads, foil/bandand mixture thereof, around the layer of longitudinal fibres; andfinishing the fabrication of the prepared blank in a second formingprocess, wherein said enveloping comprises knitting on itself, an outerlayer of a material selected from the group consisting of fibre threads,foil/band and mixture thereof, around the layer of longitudinal threads.8. The method of claim 7, wherein the final forming of the reeled bundleis carried out by tightening in a jig to the required shape and bysubsequent heating to the curing temperature of the binding agent. 9.The method of claims 7, wherein the fibre thread is selected from agroup consisting of glass, basalt, carbon, and thermoplastic.
 10. Themethod of claims 7, wherein thermoset plastic is used as a bindingagent.
 11. The method of claims 7, wherein thermoplastic is used as abinding agent.
 12. A device for reeling and winding of fibre thread forfabrication of a reinforcing blank from a composite material comprising:a rotational plate comprising a number of holding means for fibrethreads, where the holding means are arranged mutually spaced apartadjacent to the outer edge of the plate, for reeling of a blank with aclosed, approximately circular shape, comprising a layer of desiredthickness of longitudinal, parallel fibres, whereby all longitudinal,parallel fibres in the layer achieve approximately equal axialtightening, and at least one winding appliance arranged to wind amaterial selected from the group consisting of fibre threads, foil, andmixture thereof, in a helical form around the longitudinal fibrethreads.
 13. The device of claim 12, wherein the holding means consistsof wheels comprising suitable grooves for the fibre threads.
 14. Thedevice of claim 12, wherein the device comprises at least one knittingappliance arranged to knit a material selected from the group consistingof fibre threads, foil, and mixture thereof around the longitudinalfibre threads.
 15. The device of claim 12, wherein the device comprisesa tightening appliance arranged to tighten and to regulate the supply ofthe fibre thread to the holding means of the rotational plate.